Fluid pressure controlled power unit

ABSTRACT

An air powered, oil controlled power unit including a cylinder having a plunger and control valve mounted for reciprocation therein. Air from a supply source pressurizes a liquid within the plunger for displacement thereof, upon opening of a control valve by air pressure, by permitting the oil to flow from within the plunger into the cylinder. Closing of the valve immediately stops plunger displacement. The unit is provided with a displaceable, automatically controlled safety latch and a leg member to prevent rotation of the plunger relative to the cylinder. A float assembly cooperates with the valve to prevent elevation of the plunger when the oil level within the unit drops below a predetermined point.

United States Patent Crandall et al.

[4 1 Sept. 26, 1972 [54] FLUID PRESSURE CONTROLLED POWER UNIT [72]Inventors: Stanley C. Crandall, Greensboro,

NC. 27408 David B. Puryear, Summerfield, NC. 27358 [73] Assignee:Gilbert 7 8r Barker Minfic'hirifig" Company, New York, N.Y.

[22] Filed: June 1, 1970 [21] Appl. No.: 41,857

[52] US. Cl. ..91/4 A, 92/24 [51] Int. Cl. ..FlSb 21/04, FlSb 15/26 [58]Field of Search ..91/4 R, 4 A; 92/24 [56] Reierences Cited UNITED STATESPATENTS 2,471,989 5/1949 Weaver ..91/4 2,637,302 5/1953 Harrison et al...91/4 2,638,075 5/1953 Towler ..91/4 3,001,512 9/1961 Cohin ..91/43,060,900 10/1962 Pelouch ..91/4 3,447,421 6/1969 Pelouch ..91/4

FOREIGN PATENTS OR APPLICATIONS 107,350 5/1939 Australia ..91/4

Primary ExaminerPaul E. Maslousky Attorney-David Rabin [5 7] ABSTRACT Anair powered, oil controlled power unit including a cylinder having aplunger and control valve mounted for reciprocation therein. Air from asupply source pressurizes a liquid within the plunger for displacementthereof, upon opening of a control valve by air pressure, by permittingthe oil to flow from within the plunger into the cylinder. Closing ofthe valve immediately stops plunger displacement. The unit is providedwith a displaceable, automatically controlled safety latch and a legmember to prevent rotation of the plunger relative to the cylinder. Afloat assembly cooperates with the valve to prevent elevation of theplunger when the oil level within the unit drops below a predeterminedpoint.

2 Claims, 4 Drawing Figures FLUID PRESSURE CONTROLLED POWER UNITBACKGROUND, BRIEF SUMMARY AND OBJECTS OF THE INVENTION This inventionrelates to a fluid controlled power unit for supporting heavy loads, andof the type comprising a cylinder and plunger assembly, partially filledwith hydraulic fluid, and compressed air control means for regulatingthe flow of hydraulic fluid between the interior of the cylinder and theinterior of the plunger.

The power unit is particularly adapted for lifting and loweringautomobiles for servicing them by securing a super structure to theupper end of the power unit.

Present automotive lifts are generally of two basic types,semi-hydraulic lifts which use air pressure for lifting power, and fullhydraulic lifts which use air pressure to pressurize oil. The presentfull hydraulic lifts utilize large tanks either buried under the groundor set in a remote location for pressurizing the oil. However, theinstallation of such lifts is expensive due to the external tank. Thepresent semi-hydraulic lifts normally have fluid piped through a flangedportion at the bottom of the casing of the power unit. Such units aredifficult and expensive to remove and install due to the externalpiping. In addition, the semi-hydraulic lifts do not have the ability tostop at intermediate heights with any accuracy due to the air inside thelift which, when the valve is closed, must be expanded before the liftcan be stopped.

The controlled air lift of the present invention is basically a semihydraulic lift including an air actuated hydraulic valve for controllingthe ascent and descent of the lift. Air supply lines pass between thecylinder and plunger walls for pressurizing oil in the plunger and foractuating the valve which is mounted on the plunger. With the valveopened, hydraulic fluid flows between the plunger and cylinder fordisplacing the plunger upwardly or for permitting the plunger to lowerdepending upon the pressure within the plunger and cylinder. When theplunger has reached the prescribed height, the air actuated hydraulicvalve is closed stopping the lift immediately. A safety latch,associated with the air supply line controlling the air actuated valve,is retracted automatically during displacement of power unit is providedwith an internal anti-rotationdevice, and a float assembly forpreventing hydraulic fluid flow through the air actuated hydraulic valvewhen hydraulic fluid within the power unit falls below a predeterminedlevel. In addition, a plug is located within the top plate of theplunger so that compressed air within the plunger can be tapped andsupplied to drive air actuated tools.

One of the primary objects of the invention is the provision of a powerunit for lifting heavy loads in which compressed air or other similarelastic fluids are utilized in conjunction with oil or similar inelasticfluids to positively and accurately control the plunger of the powerunit.

Another object of the invention is the provision of an air-powered,oil-controlled power unit wherein fluid is piped into the top of thepower unit cylinder eliminating external piping to the lower portion ofthe power unit thereby facilitating installation and removal of theunit.

A further object of the invention is the provision of a novel safetydevice for preventing actuation of the power unit plunger when the levelof the liquid therein falls below a predetermined level.

An important feature of the invention is the provi-v sion of a powerunit having an automatically controlled safety latch located internallyof the unit to lock the plunger in prescribed positions.

Another feature of the invention is a power unit provided with anelastic fluid actuated, hydraulic valve mounted interally thereof forpositively trapping the hydraulic fluid to hold the plunger at rest inan elevated position.

Still another feature of the invention is an airpowered, oil-controlledpower unit that is safe in opera-.

tion, readily installed or removed, and maintained with minimum expense.

Other objects and advantages of the invention will become apparentduring the course of the following description.

BRIEF DESCRIPTION OF THE FIGURES DETAILED DESCRIPTION OF THE INVENTION IReferring to the drawing, the improved power unit 10 comprises, ingeneral, a cylinder 12 having a lower end closure 14 and an upper casinghead 16; a piston or plunger 18 recriprocable within the cylinder 12 andprotruding through the upper casing head 16; and compressed air conduitsfor pressurizing a body of hydraulic fluid A confined within the plungerand the cylinder and for actuating a valve 20 for controlling the flowof hydraulic fluid A between the plunger 18 and the cylinder 12.

The cylinder or casing 12, preferably formed of black iron pipe orequivalent materials, has the lower closure 14 secured therein bywelding while the upper end of the cylinder 12 receives a casing head16. The casing head 16 includes a bearing 24, an outer ring member 26welded to cylinder 12 and a wiper retaining member 22 secured to bearing24 by fasteners 23. The bearing 24 is positioned atop the cylinder 12and sealed by an O-ring 28. The outer ring member 26 is provided with arecess 25 for receiving a retaining ring 27 which is snapped in positionfor trapping the bearing 24. The wiper retaining member 22 and bearing24 have wiper members 30 and. 34 supported therein for slidably engagingthe outer wall of plunger 18 to prevent foreign material from contactingseal 32. Bearing 24 has seal 32 supported therein for slidably engagingthe outer wall of plunger 18 to prevent leakage of hydraulic fluidduring reciprocation thereof. In addition, seal 33 is locatedintermediate the outer ring member 26 and wiper retaining member 22.

To prevent rotation of the plunger 18 relative to cylinder 12, a channelor U-shaped anti-rotation leg 36 is secured within the cylinder 12 forcooperation with the lower bearing 38 of the plunger. The anti-rotationleg 36 extends vertically to a point approximately one foot below thetop of the cylinder 12 for slidably guiding the notched bearing 38 whichis secured to the plunger 18 for slidably engaging the cylinder innerwalls.

The reciprocable plunger 18, also preferably constructed of black ironpipe, has a ring 40 recessed within one end of the plunger a distancesufficient to permit nylon air supply hoses to be positioned beneath itwhen the plunger is in a lowered position. The ring 40 is secured to theinner wall of plunger 18 by a weld 42. A bottom plunger plate 44 issecured by bolts 46 or other suitable fasteners beneath the ring 40 asshown by FIG. 1. The bottom plate 44 which is sealed to the ring 40within an O-ring 48 can be removed easily to facilitate repair ofvarious components. An upper plunger'ring 50 is recessed slightly withinplunger 18 and welded thereto for receiving the top plunger plate 52fastened thereto by bolts 54. A sealing ring 56 is located between thering 50 and plate 52. The top plunger plate 52 has an opening 58provided therein in a pipe coupling 60 welded thereto. A plug 62,threaded into coupling 60 may be removed to check the level of hydraulicfluid within the plunger, or the plug may be removed and a conduitsecured to coupling 60 so that pressurized air in the plunger above thehydraulic fluid level could be tapped to provide a source of pressurizedair to drive various pneumatically operated tools.

Although not clearly shown in FIG. 3, the bearing 38, welded to theoutside of the plunger, is provided with diametrically opposed notchesor slots. One slot engages the anti-rotation leg 36 to keep the plungerfrom rotating, while the other slot allows air inlet pipes 64, 66 topass between the inner wall of cylinder 12 and the outer wall of plunger18. A stop ring 68, also slotted in the same areas the bearing 38 isslotted, is welded to the exterior of the plunger 18 for engaging thecylinder head 16 to limit the upward travel of the plunger.

The valve for controlling the flow of hydraulic fluid A between theinterior of the plunger 18 and the cylinder 12 is mounted above theplunger bottom plate 44 for reciprocation therewith. The plate 44 has aring 70 welded thereto and a plurality of small holes 72 therethroughlocated inside the ring 70. The valve 20 is held to the ring 70 with asnap ring 74 and sealed with an O-ring 76. The valve body 78, having theupper end sealed by a plug 82, houses a piston 80 having a portion 84which seats with the lower end of the valve body. A spring 86 normallyholds the valve in the closed position, however, when air enters throughplug 82 and into chamber 88, the piston head 90 pushes the portion 84downwardly permitting hydraulic fluid to flow through openings 92 in thevalve body. Preferably the valve body is made from an acetal resin andthe valve piston from stainless steel in order to provide a hard pistonin a softer valve seat area not susceptible to corrosion.

In the event the hydraulic fluid A within the plunger 18 falls below apredetermined level, a safety mechanism cooperates with the valve 20 toprevent displacement of the plunger 18 within the cylinder 12. Thesafety mechanism includes a metallic sleeve 94 and float member 96 whichare secured together and placed around the body 78 of valve 20. When thelevel of the hydraulic fluid A within the plunger 18 becomes low, thefloat, which is made of a foam material, will drop down covering theopenings 92 of the valve body shutting off fluid flow between theplunger and cylinder even when the valve is opened thus stoppingdisplacemerit of the plunger. A ring member 98 fixed to valve body 78limits upward displacement of the float member 96 when the plunger issufficiently filled with hydraulic fluid.

Air under pressure is utilized for controlling the operation of valve 20and for pressing upon the hydraulic fluid A for forcing the hydraulicfluid from within the plunger 18 into the cylinder 12 when the valve 20is open.

Compressed air is supplied from an external source, not shown, throughvalve 100, into conduit 104, through air supply junction block 105,through conduit 64 which passes between the cylinder and plunger walls,through junction block 107 and through coiled, flexible nylon hose 110.From nylon hose 110 the air under pressure passes through an opening inplunger plate 44 and upwardly through air pipe 112. The air pipe 112which extends to a height above the level of hydraulic fluid A has itslower end secured to plate 44 while the upper open end is attached tothe plunger upper ring 50 by a clamp member 114. The valve 100 is v aconventional three position, three way valve that can be locked in anyone of the neutral, pressure and exhaust positions. The air supplythrough pipe 112 to the upper part of plunger 18 can be left on forserving as a source of compressed air for operating various toolsattached to coupling 60.

For actuating the control valve 20 which is located internally ofplunger 18, air is supplied from an external source through valve 102,conduit 106, junction block 105, conduit 66, coiled nylon hose 108,safety device 116, and air line 118 into the valve body 78. Controlvalve 102 is a conventional two position valve that is spring loaded toreturn to the exhaust position thereby providing a dead man operationfor the control of the plunger 18. When the valve 102 is opened, airforces the valve piston downwardly compressing spring 86 and permittinghydraulic fluid A to flow through opening 72 and the lower plate 44 ofplunger 18 thereby displacing the plunger. Whenever the valve isreleased, it will exhaust air from the internal control valve 20 therebyclosing the valve 20 and stopping displacement of the plunger 18.

The valve 20 is designed so that fluid pressure inside the power unit atany point will close the valve regardless of whether or not the spring86 is functioning properly. If the plunger 18 is in an elevated positionand the air pressure in the top of the plunger, above the level ofhydraulic fluid A, is evacuated, the fluid pressure on the bottom of thevalve piston portion 84 is great enough to close the valve. If theplunger 18 is pressurized with air, the area on the upper part 88 of thevalve piston is greater than the area of the lower piston portion 84,insuring closure of the valve. The spring 86 is not necessary for normaloperation of the valve. However, if the plunger 18 is operated in anunloaded condition, the fluid pressure inside the power unit may not begreat enough to operate the valve satisfactorily. Therefore, the springis added to insure closure of the valve 20 at low operating pressures.The speed of the plunger 18 is controlled by the small opening 72 withinplunger plate 44.

The power unit is provided with an automatic bleed tube 120 as shown byFIG. 1. The tube 120 has its lower end 122 secured by a clamp 124 onplate 44 adjacent a low pressure area within the cylinder adjacentopening 72. They tube passes through a slot in the plunger and extendsvertically between the plunger and cylinder walls, similar to conduits64, 66 to a point adjacent the stop ring 68 where it is secured bysuitable means to the exterior of plunger 18.

The power unit 10 incorporates an internal safety latch mechanism 116thereby eliminating conventional external safety legs. The tamper proof,safety latch mechanism 116 is automatically controlled upon actuation ofvalve 20. The latch 116, mounted under the bottom plunger plate 44 fordisplacement therewith, includes a lock member 126 mounted forreciprocation within a U-shaped bracket 128 and through an opening 130in the wall of plunger 18 where it normally slides along anti-rotationleg 36. When the plunger 18 is toward the upper limit of travel the lockmember 126 will extend out over the top portion 132 of leg 36, due tothe action of coil spring 134, and due to the fluid pressure within thecylinder 12 acting upon the outer surface 137 of piston 138 therebytrapping the plunger 18 in a raised position. A connecting rod 136fastens the lock member 126 to piston 138 located within a block member140 secured to plate 44. The spring 134 acts between the block 140 andlock member 126 and normally forces the lock member 126 to an extendedposition. The control air passing from the nylon hose 108 to air line118 and valve passes through a chamber 142 within the latch block 140for withdrawing the lock member 26 during displacement of the plunger18. The air pressure in line 108, which has one end connected to block140, pushes the piston 138 to the right, as shown in FIG. 1, and pullsthe lock member 126 to an unlatched position. This happens each time thevalve 102 is opened in order to displace plunger 18. When the controlair pressure is removed from valve 20, thereby stopping and locking theplunger, the air is also evacuated from the chamber 142 of the latchblock 140. The spring 134 between the block 140 and lock member 126 andpressure of fluid A on piston surface 137 return the latch to theextended position and, if above the anti-rotation leg 36, locks theplunger 18 into position.

The safety mechanism 144 is provided to disengage the safety latchassembly 116 in the event a control air signal through conduits 108, 118cannot be provided to unlatch the lock member 126. The safety mechanismincludes a release rod 146 having the upper end 148 mounted for rotationwithin bearing 24 and having a tab 150 secured to the lower end. The rodand tab are normally biased against the cylinder inner wall by a spring152. However, when the rod 146 and tab 150 are rotated 90 degreesagainst the bias of spring 152, the tab 150 pushes the safety latchmember 126 to a disengaged position. In order to rotate the rod 146, thebleed screw 154 and ball 156 must be removed from the ring 22. At thistime, a socket head screw wrench can be placed in the socket head screw158 secured to the top of release rod 146 for rotating the rod Themanual bleed screw normally is threaded into ring 22 and seats sealingball 156 to close an opening 160 in bearing 24. Bleed screw 154 hasopenings 162 provided therein for permitting air to pass therethroughwhen the screw is rotated slightly and released from engagement withball 156.

To operate the plunger, air supply valve is opened allowing air to flowthrough conduit 104 and 64, coiled hose 110, up through air pipe 112 andinto the plunger 18 above the hydraulic fluid A therein. Thispressurizes the hydraulic fluid A in the plunger 18. However, the liftwill not move since the valve 20, which is the only opening between theplunger 18 and cylinder 12, is normally closed. When valve 102 isopened, air will flow through conduit 106 and 64, coiled hose 108,through chamber 142 of safety latch mechanism 116, through air line 118and into valve 20. The valve 20 then will open allowing hydraulic fluidA to flow from the plunger through openings 92 and 72 into the cylinder12 thus acting upon plate 44 and forcing plunger 18 upwardly. When theplunger has been displaced upwardly a desired distance, the controlvalve 102 is switched to the exhaust position thus evacuating chamber 88of valve 20 and permitting the valve to close stopping the plunger atonce. Therefore, the plunger 18, when displaced upwardly to anyposition, is supported by a column of hydraulic fluid A below plate 44,rather than air. The plunger 18 will rise no further, even if the airsupply valve 100 is in the open position. The valve 100 now can beeither left on, moved to a neutral position so that air cannot flow ineither direction, or turned to exhaust. The ability of the plunger toremain in a fixed position'is dependent only upon the internal valve 20,not on the air supply into the plunger. Also it is to noted that oncepressurized air enters the various conduits and hose leading to valve20, the lock member 126 is automatically retracted from opening 130 dueto air pressure in chamber 142. When such air pressure is exhausted,spring 134 forces the lock member back through opening 130. If theplunger is in an elevated position the member 126 will protrude over theupper portion 132 of leg 36 serving as a safety lock. During upwarddisplacement of the plunger, the coiled nylon hoses 108, are extended.Also, the anti-rotation device prevents the bottom bearing 38 fromcrushing the air supply tubes running down the inside of the cylinder.

To lower the plunger 18, air supply valve 100 is turned to exhaust airfrom within plunger 18 and then the control valve 102 is operated tosupply air to internal valve 20. The valve opens permitting fluid toflow from within the cylinder 12 into plunger through openings 72 and92. Again, when the plunger has been lowered to a selected position dueto a load acting thereon, the control valve 102 is turned to exhaust andthe valve 20 will close, stopping the plunger. Each time the valve 20'isopened, the safety latch mechanism 116 will disengage and allow the liftto be raised or lowered.

We claim:

1. In a fluid pressure actuated power unit for lifting and loweringheavy loads; a cylinder, a plunger mounted for reciprocation within saidcylinder, means on the upper end of said plunger for mounting a supportmember thereon, said cylinder and said plunger containing an inelasticfluid therein, means for introducing fluid pressure into said plungerabove the level of inelastic fluid contained therein, elastic fluidoperated means, positioned within the confines of said cylinder,regulating inelastic fluid flow between said plunger and said cylinderfor accurately controlling the position of said plunger relative to saidcylinder, said elastic fluid operated means including a fluid actuatedvalve, and means for directing fluid flow to and from said valve, and asafety latch means for trapping said plunger in a raised position, saidmeans for directing elastic fluid flow to and from said valvecooperating with said latch means for automatically retracting saidlatch means during displacement of said plunger and for permittingdisplacement of said latch means to a locking position afterdisplacement of said plunger to a prescribed location.

2. In a fluid pressure actuated power unit for lifting and loweringheavy loads; a cylinder, a plunger mounted for reciprocation within saidcylinder, means on the upper end of said plunger for mounting a supportmember thereon, said cylinder and said plunger containing an inelasticfluid therein, means for introducing fluid pressure into said plungerabove the level of inelastic fluid contained therein, an elastic fluidoperated means, positioned within the confines of said cylinder,regulating inelastic fluid flow between said plunger and said cylinderfor accurately controlling the position of said plunger relative to saidcylinder, said elastic fluid operated means including a fluid actuatedvalve, and means for directing fluid flow to and from said valve, saidmeans for introducing fluid pressure into said plunger above theinelastic fluid level and said means for directing elastic fluid flow toand from said valve includes a plurality of discrete conduit meanspositioned intermediate said cylinder wall and said plunger wall and aplurality of coiled, flexible hoses located within said cylinder.

* III II l

1. In a fluid pressure actuated power unit for lifting and loweringheavy loads; a cylinder, a plunger mounted for reciprocation within saidcylinder, means on the upper end of said plunger for mounting a supportmember thereon, said cylinder and said plunger containing an inelasticfluid therein, means for introducing fluid pressure into said plungerabove the level of inelastic fluid contained therein, elastic fluidoperated means, positioned within the confines of said cylinder,regulating inelastic fluid flow between said plunger and said cylinderfor accurately controlling the position of said plunger relative to saidcylinder, said elastic fluid operated means including a fluid actuatedvalve, and means for directing fluid flow to and from said valve, and asafety latch means for trapping said plunger in a raised position, saidmeans for directing elastic fluid flow to and from said valvecooperating with said latch means for automatically retracting saidlatch means during displacement of said plunger and for permittingdisplacement of said latch means to a locking position afterdisplacement of said plunger to a prescribed location.
 2. In a fluidpressure actuated power unit for lifting and lowering heavy loads; acylinder, a plunger mounted for reciprocation within said cylinder,means on the upper end of said plunger for mounting a support memberthereon, said cylinder and said plunger containing an inelastic fluidtherein, means for introducing fluid pressure into said plunger abovethe level of inelastic fluid contained therein, an elastic fluidoperated means, positioned within the confines of said cylinder,regulating inelastic fluid flow between said plunger and said cylinderfor accurately controlling the position of said plunger relative to saidcylinder, said elastic fluid operated means including a fluid actuatedvalve, and means for directing fluid flow to and from said valve, saidmeans for introducing fluid pressure into said plunger above theinelastic fluid level and said means for directing elastic fluid flow toand from said valve includes a plurality of discrete conduit meanspositioned intermediate said cylinder wall and said plunger wall and aplurality of coiled, flexible hoses located within said cylinder.